1. Field of Invention
The present invention relates to the disposal of waste materials which include asbestos fibers. By the present invention, waste materials which includes asbestos are permanently buried in an abandoned or inactive portion of an asbestos open pit or underground shaft mine.
2. Background and Prior Art
Both the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) have been concerned with the potential human health hazards associated with exposure to asbestos since the early 1970s. The concern is based on medical evidence relating the exposure of airborne asbestos by asbestos workers and their families to causing various types of cancer as well as noncancerous respiratory diseases.
Asbestos is a naturally occurring family of fibrous mineral substances. The typical size of respirable asbestos fibers, as illustrated relative to other substances in FIG. 1, is 0.1 to 10 microns in length, a size that is not generally visible to the human eye. Asbestos fibers occur naturally and are sold in many ranges of lengths greater than the 0.1 to 10 micron length. Respirable asbestos fibers, when disturbed, may become suspended in the air for many hours, thus increasing the extent of asbestos exposure for individuals within the area.
EPA regulations identify the following types of asbestos: chrysotile, amosite, crocidolite, anthophyllite asbestos, actinolite asbestos, and tremolite asbestos. Approximately 95 percent of all asbestos used in commercial products is chrysotile.
Asbestos became a popular commercial product because it is noncombustible, resistant to corrosion, has a high tensile strength, and some groups of asbestos fibers have a low electrical conductivity. However, asbestos had very little use until the early 1900s when it was employed as thermal insulation for steam engines. Since then, asbestos fibers have been mixed with various types of binding materials to create an estimated 3,000 different commercial products. Asbestos has been used in brake linings, floor tile, sealants, plastics, cement pipe, cement sheet, paper products, roofing products, textile products, and insulation. The amount of asbestos contained in these products varies significantly, from 1 to 100 percent, depending on the particular use.
The potential of an asbestos-containing product to release fibers to the environment is dependent upon its degree of friability. Friable means that the material can be crumbled with hand pressure. Therefore, asbestos containing materials, when friable, are likely to emit fibers. The fibrous or fluffy spray-applied asbestos materials found in many buildings for fireproofing, insulating, sound proofing, or decorative purposes are generally considered friable. Pipe and boiler wrap are also friable and found in numerous buildings.
Some materials, such as vinyl-asbestos floor tile, are considered nonfriable and generally do not emit airborne fibers unless subjected to sanding or sawing operations. Other materials, such as asbestos cement sheet and pipe, can emit asbestos fibers if the materials are subjected to breakage or crushing in the demolition or renovation of structures that contain such materials. For this reason, such materials are considered friable under the National Emission Standards for Hazardous Air Pollutants (NESHAP) regulations for the demolition of structures.
Medical studies of asbestos-related diseases have revealed that the primary exposure route is inhalation. Also, the studies suggest that there does not appear to be a safe level of exposure (e.g., a threshold) below which there would be no chance of disease.
EPA, MSHA and OSHA have major responsibility for regulatory control over exposure to asbestos. Emissions of asbestos to the ambient air are controlled under Section 112 of the Clean Air Act, which establishes the National Emission Standards for Hazardous Air Pollutants (NESHAPs). The regulations specify control requirements for most asbestos emissions, including work practices to be followed to minimize the release of asbestos fibers during handling of asbestos waste materials. These regulations do not identify a safe threshold level for airborne asbestos fibers.
The OSHA regulations are established to protect workers handling asbestos or asbestos-containing products. The current OSHA regulations include a maximum workplace airborne asbestos concentration limit of 2 fibers/cc on an 8-hour time weighted average basis, and a ceiling limit of 10 fibers/cc in any 15-minute period. The standard includes requirements for respiratory protection and other safety equipment, and work practices to reduce indoor dust levels. MSHA regulations protect miners exposed to asbestos contamination.
Wastes containing asbestos are not classified as "hazardous wastes" under the federal Resource Conservation and Recovery Act (RCRA). However, because state regulations can be more restrictive than the federal regulations under RCRA, some states are contemplating listing asbestos-containing wastes as hazardous wastes.
Asbestos has been mined and used commercially in the United States since the early 1900s. U.S. consumption of asbestos increased to a peak of 800,000 tons per year in the early 1970s. Since then, consumption has dropped by more than 70 percent. However, much of the material originally installed in buildings may still be present.
Some typical uses of asbestos for brake linings are in automobiles, buses, trucks, railcars, and industrial machinery, and in vehicle or industrial clutch linings. Asbestos-containing brake linings include drum brake linings, disc brake pads, and brake blocks. In the past, asbestos linings have accounted for up to 99 percent of this market. Friction materials are generally tough and nonfriable, but they release asbestos dust during fabrication operations. In addition, accumulated dust in a brake drum from lining wear contains asbestos. Thus, brake installation facilities (e.g., city bus service centers, tire and brake shops) generate significant quantities of asbestos waste. Safe transport and permanent disposal of this waste has been a problem of the industry.
Plastic products which contain asbestos include resilient vinyl and asphalt floor coverings, asphalt roof coatings, and traditional molded plastic products such as a cooking pot handle or plastic laboratory sink. The products in this category are usually tough and inflexible. The asbestos in these products is tightly bound and is not released under typical conditions of use. However, any sawing, drilling, or sanding of these products during installation or removal results in the release of asbestos dust and potentially harmful asbestos waste products.
Asbestos-cement (A-C) pipe has been widely used for water and sewer mains, and is occasionally used for electrical conduits, drainage pipe, and vent pipes. Asbestos-cement sheet, manufactured in flat or corrugated panels and shingles, has been used primarily for roofing and siding, but also for cooling tower fill sheets, canal bulkheads, laboratory tables, and electrical switching gear panels. The asbestos in these products is tightly bound, and would not be released to the air under typical conditions of use.
However, any sawing, drilling or sanding of these products during installation or renovation could result in release of asbestos dust. In addition, the normal breakage and crushing involved in the demolition and renovation of structures can release asbestos fibers from these materials. For this reason they are subject to the NESHAPs regulation during demolition and renovation operations. Also, normal use of A-C pipe for water or sewer mains has been shown to release asbestos fibers to the fluid being carried. Therefore, an ongoing process has been initiated to replace A-C pipe products. A problem has arisen with finding a suitable permanent disposal site for these waste products.
Roofing felts, gaskets, and other paper products are manufactured on conventional papermaking equipment using asbestos fibers instead of cellulose. The raw asbestos paper produced in this process has a high asbestos content (approximately 85 percent), but is typically coated or laminated with other materials in the final product. The asbestos fibers in most paper products are sufficiently bound to prevent their release during normal product use.
However, cutting or tearing the material during installation, use, or removal can result in the release of asbestos dust. Therefore, the asbestos waste products created during demolition or renovation of a building, to remove the potentially harmful asbestos waste products, have presented a problem of finding a safe, permanent disposal site.
Asbestos yarn, cloth and other textiles are made using conventional textile manufacturing equipment. These materials are used to manufacture fire-resistant curtains or blankets, protective clothing, electrical insulation, thermal insulation, and packing seals. The raw textile products have a high asbestos content (approximately 85 percent). However, they are typically coated or impregnated with polymers before assembly into a final product, which is not required to be labeled as containing asbestos and typically is not so labeled. These products may release asbestos dust if cut or torn, or for some products, during normal use. There still remains a significant quantity of non-coated asbestos fabrics in use, especially in schools and fire departments. The ongoing process of eliminating these fabrics has created a vast source of asbestos-containing waste materials.
Asbestos-containing thermal insulation generally refers to sprayed and trowelled asbestos coatings, and molded or wet-applied pipe coverings. These materials generally have an asbestos content of 50 to 80 percent. The coatings were commonly applied to steel I-beams and decks, concrete ceilings and walls, hot water tanks and boilers. The coatings were applied primarily for thermal insulation, although in many cases the coating also provided acoustical insulation and a decorative finish.
Sprayed coatings typically have a rough, fluffy appearance, while trowelled coatings have a smooth finish and may be covered with a layer of plastic or other non-asbestos material. Both sprayed and trowelled asbestos coatings are considered friable in most applications. Most spray-applied asbestos coatings were banned for fireproofing/insulating in 1973, and for decorative purposes in 1978. Efforts are presently underway to remove these coating from schools and other public buildings to avoid the possibility of airborne asbestos contamination.
Asbestos insulation board was used as a thermal/fireproofing barrier in many types of walls, ceilings, and ducts or pipe enclosures. This material looks like A-C sheet, but is less dense and much more friable. High asbestos dust levels have been measured for many board handling operations, including a simple unloading of uncut sheets. These sheets are presently being removed from public places.
Preformed pipe coverings having an asbestos content of about 50 percent were used for thermal insulation on steam pipes in industrial, commercial, institutional, and residential applications. The installation of wet-applied and preformed asbestos insulation was banned in 1975; however, significant amounts are typically found in older structures.
Preformed block insulation was used as thermal insulation on boilers, hot water tanks, and heat exchangers in industrial, commercial, institutional, and residential applications. Asbestos block insulation is friable and rapidly deteriorates in a high humidity environment or when exposed to water. The installation of this type of asbestos insulation was banned by EPA in 1975.
Other uses of asbestos have included: exterior siding shingles, shotgun shell base wads, asphalt paving mix, spackle and joint patching compounds, artificial fireplace logs for gas-burning fireplaces, and artificial snow. The use of asbestos as artificial logs in gas-burning fireplace systems was banned in 1977, while the use of asbestos as an ingredient in spackle and joint compounds was banned in 1978.
Asbestos-containing wastes are generated by a variety of processes, including mining and milling asbestos ore and manufacturing and fabricating asbestos products. In addition, ever increasing efforts are being made to remove all forms of asbestos from demolition or renovation operations to prevent exposure to the public of asbestos containing waste. This is generating huge quantities of waste materials which include asbestos contamination.
Asbestos is "manufactured" by mining the ore deposit and separating the fibers from the non-asbestos rock. Some of the active asbestos mines in the United States, are located near Copperopolis and Coalinga, Calif., and Hyde Park, Vt. Seven other mines which were closed in the 1970s are located across the United States with three in Arizona, two in California, and two in North Carolina.
The process of separating asbestos fibers from the mined ore, and grading and packaging these fibers according to length, is called milling. Mills also generate asbestos-containing waste from air cleaning control devices used to meet EPA and OSHA requirements. EPA requires all asbestos-containing wastes from mills to be disposed without any visible emissions to the outside air, or certain wetting practices must be used to control emissions.
Asbestos mines generate a large quantity of waste rock, called tailings, having insufficient asbestos content for additional processing. Additional tailings are produced by a milling process. Both types of tailing waste are typically piled in an area adjacent to the mine. Tailings are usually disposed by loading on a conveyor belt and dumping on an onsite waste pile. Overburden includes soil and other material which masks the ore and is usually included with the tailings pile. Emission control during transport and dumping of tailings is usually achieved by wetting, although local exhaust ventilation may occasionally be used.
Asbestos products are manufactured by combining the milled asbestos fibers with binders, fillers, and other materials. The resultant mixture, which may be either dry or wet, is molded, formed or sprayed, and then cured or dried. Some products require further machining or coating operations prior to their sale. Manufactured products may then be fabricated by another manufacturer, by the installer or final consumer.
Manufacturing and fabricating operations generate the following asbestos-containing wastes:
(1) empty asbestos shipping containers; PA1 (2) process wastes such as cuttings, trimmings, and off-specification/reject material; PA1 (3) housekeeping waste from sweeping or vacuuming; and PA1 (4) pollution control device waste from dust capture systems. PA1 (1) A separate area is selected for asbestos waste disposal and a record is provided for future landowners that asbestos waste has been buried there and that it would be hazardous to attempt to excavate that area. PA1 (2) A trench is prepared to receive the asbestos wastes. The size of the trench will depend upon the quantity and frequency of asbestos waste delivered to the disposal site. The trenching technique allows application of soil cover without disturbing the asbestos waste containers. The trench should be ramped to allow the transport vehicle to back into it, and the trench should be as narrow as possible to reduce the amount of cover required. If possible, the trench should be aligned perpendicular to prevailing winds. PA1 (3) The asbestos waste containers are then carefully placed into the trench to avoid breaking them. Particular care should be exercised with plastic bags because when they break under pressure, asbestos particles can be emitted. PA1 (4) The containerized waste should then be completely covered within 24 hours with a minimum of 6 inches of non-asbestos material.
Process and manufacturing wastes containing asbestos are wetted before packaging using a mixture of surfactant (e.g., soap) and water, in a fine mist. Empty shipping bags can be flattened and packaged under hoods exhausting to a pollution control device. Empty shipping drums are difficult to thoroughly clean, and should be sealed and disposed of or used to contain other asbestos wastes for disposal. Air pollution control device waste is usually packaged directly by connecting a container to the waste hopper outlet. Vacuum bags or disposable paper filters are not cleaned, but rather are sprayed with a fine water mist and placed intact into a proper container.
A very large quantity of asbestos-containing waste is currently generated from the removal of friable asbestos materials from buildings to be demolished or renovated. EPA regulations address the removal of friable asbestos materials prior to demolition or renovation of buildings in the Code of Federal Regulations (40 CFR Part 61, Subpart M). Removal is also considered for materials that may potentially become friable during the demolition or renovation activities. Currently, the federal regulations apply to larger structures, i.e., structures with more than four apartments, with certain minimum quantities of asbestos-containing material. However, some state and local health agencies require removal of lesser quantities of asbestos from smaller buildings.
When the asbestos materials are prepared for removal, they are wetted with a water and surfactant mixture sprayed in a fine mist, allowing time between sprayings for complete penetration of the material. Once the thoroughly wetted asbestos material has been removed from a building component, EPA and OSHA regulations require the wastes to be containerized as necessary to avoid creating dust during transport and disposal. The generally recommended containers are 6-mil thick plastic bags, sealed in such a way to make them leak-tight. More thorough containerization may include double bagging, plastic-lined cardboard containers or plastic-lined metal containers. Asbestos waste slurries can be packaged in leak-tight drums if they are too heavy for the plastic bag containers. Both EPA and OSHA specify that the containers be tagged with a warning.
The safe, permanent disposal of the enormous quantities of asbestos contained waste material currently being generated is becoming a major health and disposal problem. Current disposal of asbestos waste involves the isolation of the asbestos waste material in order to prevent fiber release to air or water. One recommended technique is landfilling by which the asbestos fibers are buried in soil. Other disposal techniques such as incineration or chemical treatment have not proven viable to date due to the unique properties of asbestos. EPA has established asbestos disposal requirements for active and inactive disposal sites under NESHAPs (40 CFR Part 61, Subpart M) and specifies general requirements for solid waste disposal under RCRA (40 CFR Part 257).
Recognizing the health dangers associated with asbestos exposure, the following procedures are recommended by the EPA to augment current EPA requirements for the burial of asbestos-containing waste:
Current costs for the disposal of asbestos-containing waste are running at about a minimum of $40/cu. yd. with some disposal costs running as high as $159/cu. yd.
The problems discussed above are addressed and overcome by the present invention.